At Ad Age, Elizabeth Wilner writes about the historic role of American Crossroads, Restore Our Future, Crossroads GPS and Americans for Prosperity:
Between April and August, Romney had fewer resources to devote to advertising. To the extent that the race "broke" temporarily for President Barack Obama, it only happened in September. By keeping the heat on Obama and amplifying every drag on the country's slow-healing economy, these groups kept the race tight for four months and, for the most part, continue to boost Romney today. Americans for Prosperity did its heavy lifting for Romney back in August and early September; the other three are still on the air in a big way.
[T]hese groups helped facilitate the historic shrinking of the swing-state map. Along with Priorities USA Action, the GOP super groups carried out the testing of other possible battlegrounds beyond the original eight states. They were the first ones into Wisconsin; the nominees eventually followed. They sponsored the TV advertising in Pennsylvania before that state was sidelined in Democrats' favor; Romney never advertised there. Even now, they continue to carry his water in Michigan and Minnesota.
With the super groups able to advertise in states that may be more of a reach for one side or the other, the nominees' campaigns have now been able to focus on just nine states all the way up until mere days before Election Day, without having to decamp from any of them. In the olden days of 2004 and 2008, late October typically brought tough decisions about pulling ad spend from some states in order to shore up others. In 2012, the campaigns have the luxury of not having to make those decisions.
This tiered approach -- with campaigns focusing on states fully in play and super groups taking on the rest -- has resulted in a 2012 presidential advertising battlefield that has stayed remarkably stable and compact. On October 19, 2008, 112 markets saw presidential advertising on broadcast TV. Four years later, that number was cut nearly in half: 61 markets saw presidential advertising on broadcast TV on October 19.